A radiotelephone/facsimile combination allows a user to transmit and receive documents without having the constraints of a fixed office. A radiotelephone/computer combination permits a computer user to access a data base or to contact other computer users with a portable computer, also without being tied down to an office. If the computer has the proper modem, documents can also be sent from the computer to a facsimile machine. A typical radiotelephone is described in detail in Motorola Micro T.A.C manual #68P81150E49 available from the assignee of the present invention.
The problem with these schemes, however, is that these combinations are typically powered by a car's electrical system. To remain truly mobile, the radiotelephone/facsimile or radiotelephone/computer must be battery powered, allowing the user to take the combinations anywhere. This results in the combinations being powered by either one battery for both units of the combination or separately powering each unit with separate batteries, requiring a larger and heavier combination. With either power scheme, both units of the combination must either remain powered up to receive an incoming call or the facsimile or computer turned on manually when a telephone call is received that requires those units. In either case, the battery's usefulness will decrease due to the time the units are on and not being used. Even if the units are turned on and off manually when a call is received, there is still the possibility of it being inadvertently left on and draining the battery.
A radiotelephone/computer user may also want to send data out via a modem that is connected to the radiotelephone. In this case the radiotelephone must be left on or turned on and off manually when it is needed. There is a resulting need for a radiotelephone/computer or radiotelephone/facsimile combination that conserves battery power when not active.